In this paper, we present an extension to NS3 that allows simulating different jamming scenarios for cognitive radio networks (CRNs). The extension includes an adjustment to the physical and MAC layers of the existing NS3 Wi-Fi module to include the unique features of CRNs including the licensed primary user activities and channel quality. Up to our knowledge, this is the first NS3 implementation to support jamming attacks for CRNs. The paper demonstrates the implementation details along with the results of running different jamming and anti-jamming scenarios in CRN environments.